The present invention concerns generally a medical device. More specifically, the present invention concerns a therapeutic catheter for treatment of vessels in a patient. The present invention includes catheters having proximal sensors for measuring changes at the distal end of the catheter.
A therapeutic catheter having at last two channels or lumens extending through it in the longitudinal direction is known from EP-A-0 527 312 (corresponds to DE 41 26 886 A1). One lumen is a flow channel to supply liquid with high pressure (for example, 75 bar), from the near or proximal end to the far or distal end of the catheter. The catheter has an open flow path on its distal end at which the liquid in the form of a sharp jet can separate parts of a body tissue in a patient and convey them into the other lumen, which serves as return channel and transports the liquid together with the separated tissue material to the proximal end of the catheter. A similar or therapeutic catheter is also known from the published Patent Application DE 42 01 992 A1. Other known therapeutic catheters, like the one known from U.S. Pat. No. 5,380,273, have one or even two expansion elements, so-called dilation balloons, on the distal end with which blood vessels in a patient can be dilated or blocked. Moreover, mechanical catheters with a rotating tool on their distal end section to remove material in vessels of a patient are known from U.S. Pat. No. 5,092,872 and the unexamined German Applications DE 38 01 318 A1, DE 38 28 478 A1 and DE 43 23 756 A1. PCT-WO 89/09029 also exhibits a mechanical catheter with pivotable tools on the distal catheter end.
During introduction of a catheter into a patient the physician can observe the position of the catheter on an x-ray screen. However, the tissue or condition of the tissue is not recognizable or not clearly recognizable on the x-ray screen. The physician is therefore not capable of checking the therapeutic success on-line during therapy. He receives no feedback as to whether a vascular obstruction, for example, has been sufficiently eliminated. He is forced to adopt an iterative procedure xe2x80x9ctherapy, control, therapy, and so forthxe2x80x9d in which the physician must rely on his experience and feelings in establishing the control intervals. This procedure leads to frequent control angiographies which expose the patient to radiation and contrast agents.
To summarize, this means that, when therapeutic catheters of the aforementioned types are used combined with x-ray imaging devices, the user only receives information concerning the position of the catheter in the patient, but the actual therapeutic function is not visible.
A hydrodynamic thrombectomy catheter in which fluid is guided via a channel system to treat the patient tissue and ultrasound is guided via a separate system to the tip of the catheter for optical monitoring of catheter operation is known from EP 0 483 133 A1. The therapy channel for the fluid and the diagnosis channel for the ultrasound diagnosis are separate and independent of each other.
In catheters in which laser radiation or ultrasound is used to treat patient tissue, the function of the catheter tip in a patient tissue can be monitored simply by reflecting laser beams or ultrasound waves. Such catheters are known, for example, from the following documents: publication of the article xe2x80x9cLaser-induced Shockwave Lithotripsy with Microsecond Laser Pulsesxe2x80x9d in the journal Laser und Optoelektronik 20(4)/1988 by R. Engelhardt, W. Meyer, S. Thomas, P. Oehlert; published Patent Applications DE 43 22 955 A1 and DE 195 22 310 A1; Patent DE 42 40 182 C2, U.S. Pat. No. 5,104,392 and EP 0 582 766 A1. Moreover, a therapeutic catheter for treatment of patent tissue with laser light having an additional internal hollow channel to which a laser beam is transmitted for diagnostic purposes is known from DE 44 37 578 A1. Several therapeutic catheters are also known from EP 0 629 380 A1: a catheter for elimination of stenoses by laser radiation, a catheter with an expandable balloon on the distal end of the catheter to eliminate stenoses, and a catheter to treat patient vessels with ultraviolet light to prevent new formation of stenoses in blood vessels of the patient. No diagnostic possibilities are provided in these last-named catheters.
The invention is supposed to solve the task of devising a possibility in catheters having fluid channels and/or mechanical tools for therapeutic treatment of patient vessels, through which a signal can be generated in simple fashion, providing the user with information concerning the therapeutic effect of his work with the catheter in a patient.
Catheters according to the present invention can include a fluid channel extending at least from the proximal end to the distal end, and in some embodiments, return from the distal end to the proximal end. External changes in environment of the fluid in the distal end section of the catheter can cause one or more physical values or value changes to the fluid. The value changes can be measured at the proximal end of the catheter.
In one aspect of the invention, sensors or measurement devices on the proximal section of the catheter can measure physical changes in the fluid which are caused by external conditions acting on the fluid in the distal section of the catheter. In one embodiment, the distal section has an expandable element such as an inflatable balloon which can be inflated by fluid in the fluid channel. Sound or pressure can be measured at the proximal end of the catheter. In another embodiment of the invention, the distal section can include an open portion having hydrodynamic jet which can be used to break up a vessel occlusion and sweep broken pieces proximally through the fluid channel. Sound or pressure changes in the fluid caused by changes at the distal end can be measured at the proximal end. In yet another embodiment, a rotating tool at the distal end can be driven by a rotating shaft extending from the distal end to the proximal end. Changes in torque at the proximal end can be measured. The proximally measured changes can be output as optically or acoustically recognizable signals or values. Some embodiments have an acoustic signal generator for converting the detected or measured values into acoustic signals audible to persons.
The fundamental idea of the invention is as follows: when therapeutic catheters are used in which the energy is transported in the form of a liquid or gaseous fluid under pressure or in the form of mechanical energy from the proximal end section to the distal end section, especially to the catheter tip of the catheter and used there for therapy in a patient, the energy is altered by feedback from the patient tissue. Or in other words, the magnitude and type of energy released at the catheter tip to the surroundings is changed by feedback from these surroundings to this energy. In a gaseous or liquid fluid under pressure for removal of material in patient vessels, the pressure of the fluid is changed as a function of the flow resistance of the fluid between the distal end section of the catheter and its surroundings, which is formed by the patient tissue.
Noise also develops in the fluid stream and thus sound waves as a function of whether the fluid encounters patient tissue and/or ablates the patient tissue and/or the ablated or cut patient tissue is drawn by the fluid into the fluid channel. These pressure changes and/or noise or sound waves occurring on the distal end section of the catheter are determined according to the invention on the proximal end section of the catheter by a sensor or measurement device and made acoustically audible or visually visible for an operating person of the catheter. Because of this the operating person with reference to this acoustic or optical signal can recognize whether the fluid and in which way the fluid is acting on a patient tissue in a patient. In similar fashion the torque and/or noise developments of a drive shaft, which drives a rotating tool on the distal end of the catheter, are measured by the invention during use of mechanical catheters in the therapeutic treatment of patient vessels. An acoustic and/or visible signal or measurement result is generated as just described from these measurements, with reference to which an operating person can recognize and evaluate the effect of the rotating tool on a patient vessel in a patient. These changes in energy in the form of pressure changes, sound generation or sound changes or torque and torque changes which occur on the distal end section of the catheter, are determined or measured by the invention on the proximal end section of the catheter, during which this measurement is conducted in the same fluid or in the same mechanical element on the proximal end section of the catheter that conveys the energy to the distal end section of the catheter. Thus, according to the invention, the same channel and the same fluid or the same mechanical element is used for therapy of the patient as for signal production. By connecting a sensor or measurement element to the fluid channel or the mechanical drive element on the proximal end section of the catheter the aforementioned changes are recorded and made visible and/or audible to the user. The treatment medium xe2x80x9cfluidxe2x80x9d or xe2x80x9cdrive elementxe2x80x9d thus has a dual function, in which it serves both for therapy and energy transmission from the proximal end section to the distal end section of the catheter and in the opposite direction as an information path from the distal end section to the proximal end section of the catheter. No information path in addition to the therapy path is required for information transmission.
Additional features of the invention are contained in the subclaims.